The studies outlined in this application will explore the relationship of colonic glycoprotein composition and structure to inflammatory bowel disease (IBD). In recent studies in this laboratory purified human colonic mucin was found to consist of a mixture of at least six distinct mucin species (I-IV). In contrast, mucin from patients with ulcerative colitis (UC) revealed a selective reduction of one mucin subclass (species IV). Analysis of mucin composition in colonic mucosal biopsies using radiolabeling techniques has confirmed the specificity of this association. The selective reduction in species IV in UC was also found during remission as well as in mucin from uninvolved colonic mucosa of patients with UC. These data suggest that there may be an underlying structural defect in colonic mucin in UC. This proposal outlines studies to extend these observations on mucin glycoproteins and to evaluate the structure and function of non-mucin colonic glycoproteins. Serial studies in UC patients using methods developed to radiolabel mucin will be used to delineate the relationship of alteration in mucin and disease activity. Mucin composition will be assessed in first degree relatives of patients with IBD to examine any possible genetic basis for observed alteration in mucin composition. Composition and structure of purified mucin species will be determined; using high pressure liquid chromatography (HPLC) and gas chromatography-mass spectroscopy technology. In addition mucin subspecies specific antibodies will be developed using hybridoma technology to facilitate studies on mucin species localization and goblet cell function. Fluorescent labeling techniques should delineate changes in mucin composition in health and disease. Finally, non-mucin glycoproteins from both normal and IBD colonic tissue will be characterized in studies paralleling those with mucin glycoproteins. Thus, a comprehensive study of colonic glycoproteins is proposed to enhance our understanding of their composition, function and contribution to inflammatory bowel disease.